The pineal gland is a 12mm long structure located within the center of the human brain and is as small as a pea, surrounded by cerebrospinal fluid. It is in a tiny cave, behind and above the pituitary gland, which lies a little behind the root of the nose. It is located directly behind the eyes, attached to the third ventricle. This gland isactivated by light, and it controls the various biorhythms of the body. It works in harmony with the hypothalamus gland, which directs the body’s thirst, hunger, sexual desire and the biological clock, that determines our aging process. When the pineal gland awakens, one feels a pressure at the base of the brain. This pressure will often be experienced, when connecting to higher frequency or level of consciousness. While the physiological function of the pineal gland, has been unknown until recent times, mystical traditions and esoteric schools, have long known, this area in the middle of the brain, to be the connecting link between the physical and nonphysical (spiritual) planes of existence. The gland weighs little more than 0.1 gram. (Source)